Weight painting seems to be ignored on my rig
Found 2 issues here :


First, you forgot to apply the mirror modifier.
Second, you can see that it is not the "foot" weight that influences the other side, but the "toe" weight (and this is a side-effect of the mirror modifier I guess) :




So make sure to apply the mirror modifier before parenting the armature, then try again. You'll be able to tweak the weight painting more efficiently.

And a side note, you'd better to pull up the Armature modifier before the Subsurf modifier (you'll get better performance while moving the rig, so the animation will be less painful;)